The present invention relates to a display, and especially a color display, which comprises an organic electroluminescent light emitting device (which will hereinafter be often called an organic EL device for short) using an organic compound.
In recent years, organic EL light emitting devices have been under intensive investigation. Basically, this device is made up of a hole injecting electrode such as a tin-doped indium oxide (ITO) electrode, a hole transporting material film such as a triphenyldiamine film formed thereon, a light emitting layer formed of a fluorescent material such as an aluminum quinolinol complex (Alq3) and laminated on the hole transporting film, and a metal electrode (electron injecting electrode) formed of a metal having a low work function such as Mg and provided on the light emitting layer. Such an organic EL device attracts attentions because they can achieve a very high luminance ranging from a few hundred to tends of thousands of cd/m2 with a driving voltage of approximately 10 volts.
Displays constructed using such an organic EL device may potentially have various applications, and its application to color displays in particular is an important challenge. When a light emitting device is applied as a color display, for instance, it is a common procedure to vary the color of light emitted from the light emitting device or use color filters to obtain the three primary colors, blue, green and red.
One known approach to varying the color of light emitted from a light emitting device itself is embodied by a color light emitting device as typically set forth in SID 96 DIGEST.185 14.2: Novel Transparent Organic Electro-luminescent Devices G. Gu, V. B. Bulovic, P. E. Burrows, S. R. Forrest, M. E. Tompson. However, this color light emitting device (heterostructure organic light emitting device) has a multilayer structure comprising light emitting layers (Red ETL, Green ETL and Blue ETL) corresponding to the three primary colors, R, G, and B, respectively. One problem with this device is that its structure becomes complicated with a production cost increase because a cathode and an anode must be provided for each light emitting layer. Another problem is that the color balance is disturbed with use due to a service life difference between the three primary colors.
On the other hand, a color display constructed using a single light emitting device in combination with a fluorescence converting layer formed of a fluorescent material and/or a color filter layer may be a good system, because a simple and inexpensive arrangement is not only achievable by use of a single organic EL device alone but also full-color displays are obtainable by forming the fluorescence converting layer and/or color filter layer according to a given pattern. In view of patterning technologies, damages to the organic EL structure, etc., however, it is very difficult to provide the fluorescence converting layer and/or color filter layer on the organic EL structure according to a predetermined pattern. When an organic EL device is constructed by patterning the fluorescence converting layer and/or color filter layer on the organic EL structure provided on a substrate, the organic EL device cannot perform its own function, because there is a step between the organic EL structure and the fluorescence converting layer and/or color filter layer. This step causes breaks in the film (discontinuities in the film), which make wiring impossible, resulting in a current failure.
An object of the present invention is to provide an organic EL color display which can be fabricated easily and at low costs yet with high reliability.
Such an object is accomplished by the inventions defined below.
(1) An organic EL color display comprising a substrate and, in order from said substrate, a fluorescence converting layer containing a fluorescent material and/or a color filter, layer an organic layer, a barrier layer and an organic EL structure, wherein:
said organic layer is formed of a thermosetting resin or an ultraviolet curing resin, and
said barrier layer contains silicon oxide.
(2) The organic EL color display of (1), wherein said barrier layer has an average surface roughness (Ra) of 2 to 50 nm.
(3) The organic EL color display of (1), wherein said barrier layer has been subjected to a plasma treatment.
(4) The organic EL color display of (1), wherein said organic layer is formed of an acrylic resin.
(5) The organic EL color display of (1), wherein said barrier layer has a refractive index of 1.40 to 1.55 at a wavelength of 632 nm.
(6) The organic EL color display of (1), wherein said silicon oxide is represented by SiOx where x=1.8 to 2.2.
(7) The organic EL color display of (1), wherein said silicon oxide is represented by SiOx where x=1.5 to 1.9, and contains at least one of carbon and nitrogen in an amount of up to 20 at % as calculated on C and N bases.
(8) The organic EL color display of (1), wherein said barrier layer has an emitted light transmittance of at least 80%.
(9) The organic EL color display of (1), wherein said barrier layer has been formed by a sputtering process.